1. Technical Field
The present invention relates to a projector including a first spatial modulation element and a second spatial modulation element which are disposed in series on a light path.
2. Related Art
A projector is known in which two spatial modulation elements are arranged in series in order to increase image contrast (for example, refer to JP-A-2007-218946). In this case, a relay lens is disposed between the two spatial modulation elements, and one image of the two spatial modulation elements is superimposed on the other image so as to form an image.
In JP-A-2007-218946, two or more spatial modulation elements are disposed in series, and both spatial modulation elements are made to have a substantial image formation relationship (here, the image formation relationship indicates an arrangement relationship in which the spatial modulation elements mutually form an image) in a relay optical system. Therefore, in order to improve contrast in an image, the relay optical system does not completely superimpose one image of the two spatial modulation elements on the other image so as to form an image. Consequently, moire due to black matrices between pixels of the spatial modulation elements is minimized. In addition, in a projector, other techniques are known in which two spatial modulation elements are arranged in series so as to increase contrast in an image (refer to JP-T-2006-509244, JP-A-2005-189282, and JP-A-2005-208573). For example, in JP-T-2006-509244, when an image is formed by superimposing one image of two spatial modulation elements on the other image, a double Gauss lens is used as a relay lens.
However, for example, in JP-A-2007-218946, if a desired defocus state is to be maintained, that is, a positional relationship in which one image is not completely superimposed on the other image is to be maintained as well as making the two spatial modulation elements have a substantial image formation relationship, position accuracy (that is, manufacturing tolerance) becomes strict, and thus there is a probability that position adjustment may be difficult. Since a distribution of a defocused image (blurred image) varies depending on a variation in a distribution of light from a light source, there is a probability that an image may be disturbed due to influence of the light distribution. This also occurs in the other documents as well as JP-A-2007-218946.